Ketamine/Xylazine is more often use as a mean of anesthesia for terminal protocols, eg. for cardiac perfusion before dissection. Rodents will die from Ketamine/Xylazine overdose. You should induce and maintain your anesthesia with isoflurane if you need to keep your animals alive after anesthesia. If not possible, you can reduce the Ketamine/Xylazine dose.

I would suggest that you read George Washington Crile’s classic book called “Anoci-Association” that is available via the Internet. Crile explains why anesthesia must be supplemented with analgesia in order to minimize surgical stress. Also read Yandell Henderson’s classic papers describing the therapeutic benefits of carbon dioxide. Analgesia prevents harmful nociception, which stimulates hyperventilation that dangerously depletes carbon dioxide. Ketamine, Propofol, and Sevoflurane are all anesthetic agents with no analgesic properties. You are not adequately protecting your rats from stress.

what dose of xylazine and ketamine you use ?